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Ruby Accessors & Attributes Mastery

Ruby's accessor methods provide elegant ways to define getter and setter methods for instance variables. Master attr_reader, attr_writer, attr_accessor, and custom attribute methods for clean, maintainable code.

Basic Accessor Methods

Accessor Methods: Ruby provides three built-in accessor methods to automatically generate getter and setter methods for instance variables.

attr_reader - Read-Only Access

# attr_reader creates getter methods only
class
Person
  attr_reader :name, :age
  
  def initialize(name, age)
    @name = name
    @age = age
  end
end

person = Person.new("Alice", 25)
puts
person.name
# "Alice"
puts
person.age
# 25
# person.name = "Bob"  # NoMethodError!

attr_writer - Write-Only Access

# attr_writer creates setter methods only
class
Config
  attr_writer :api_key, :timeout
  
  def initialize
    @api_key = "default"
    @timeout = 30
  end
end

config = Config.new
config.api_key = "secret123"
config.timeout = 60
# puts config.api_key  # NoMethodError!

attr_accessor - Read/Write Access

# attr_accessor creates both getter and setter methods
class
User
  attr_accessor :name, :email, :active
  
  def initialize(name, email)
    @name = name
    @email = email
    @active = true
  end
end

user = User.new("Alice", "alice@example.com")
puts
user.name
# "Alice"
user.name = "Alice Smith"
user.active = false
puts
user.active
# false

Custom Accessor Methods

Custom Accessors: Override default accessor behavior with validation, formatting, and custom logic.

Custom Getter with Formatting

# Custom getter with formatting
class
Product
  attr_reader :name
  
  def initialize(name, price)
    @name = name
    @price = price
  end
  
  def price
    "$%.2f" % @price
  end
end

product = Product.new("Laptop", 999.99)
puts
product.price
# "$999.99"

Custom Setter with Validation

# Custom setter with validation
class
BankAccount
  attr_reader :balance
  
  def initialize(initial_balance)
    @balance = initial_balance
  end
  
  def balance=(amount)
    raise "Balance cannot be negative" if amount < 0
    @balance = amount
  end
end

account = BankAccount.new(1000)
account.balance = 1500
puts
account.balance
# 1500
# account.balance = -100  # RuntimeError!

Interactive Practice: Accessors & Attributes

Practice Time: Try these accessor and attribute examples. Understanding these patterns will make you a more effective Ruby programmer.

Interactive Code Runner

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# Try these comprehensive accessor examples!

# 1. Basic accessors
class Person
  attr_reader :name, :age
  attr_writer :email
  attr_accessor :active
  
  def initialize(name, age, email)
    @name = name
    @age = age
    @email = email
    @active = true
  end
end

person = Person.new("Alice", 25, "alice@example.com")
puts person.name  # "Alice"
puts person.age   # 25
person.email = "alice.new@example.com"
person.active = false
puts person.active  # false

# 2. Custom accessors with validation
class Student
  attr_reader :name, :grades
  
  def initialize(name)
    @name = name
    @grades = []
  end
  
  def grade=(score)
    raise "Grade must be between 0 and 100" unless (0..100).include?(score)
    @grades << score
  end
  
  def average_grade
    return 0 if @grades.empty?
    @grades.sum.to_f / @grades.length
  end
end

student = Student.new("Bob")
student.grade = 85
student.grade = 92
student.grade = 78
puts "Average: #{student.average_grade.round(2)}"  # 85.0

# 3. Computed attributes
class Rectangle
  attr_accessor :width, :height
  
  def initialize(width, height)
    @width = width
    @height = height
  end
  
  def area
    width * height
  end
  
  def perimeter
    2 * (width + height)
  end
  
  def square?
    width == height
  end
end

rect = Rectangle.new(5, 5)
puts "Area: #{rect.area}"        # 25
puts "Perimeter: #{rect.perimeter}"  # 20
puts "Square? #{rect.square?}"      # true

# 4. Virtual attributes
class Temperature
  attr_reader :celsius
  
  def initialize(celsius)
    @celsius = celsius
  end
  
  def fahrenheit
    (celsius * 9.0 / 5) + 32
  end
  
  def fahrenheit=(f)
    @celsius = (f - 32) * 5.0 / 9
  end
  
  def kelvin
    celsius + 273.15
  end
  
  def kelvin=(k)
    @celsius = k - 273.15
  end
end

temp = Temperature.new(25)
puts "Celsius: #{temp.celsius}"      # 25
puts "Fahrenheit: #{temp.fahrenheit}"  # 77.0
temp.fahrenheit = 86
puts "Celsius: #{temp.celsius}"      # 30.0

# Add your own accessor experiments below!

Output will appear here when you run the code...

Best Practices & Common Patterns

✅ Best Practices

Use attr_reader for read-only attributes
Use attr_writer for write-only attributes
Use attr_accessor for read/write attributes
Override accessors for validation and formatting
Use virtual attributes for computed values
Keep accessor methods simple and focused

❌ Common Pitfalls

Overusing attr_accessor without validation
Not handling edge cases in custom accessors
Creating circular dependencies in accessors
Forgetting to call super in overridden accessors
Making accessors too complex
Not documenting custom accessor behavior

Accessors & Attributes Mastery Summary

You've Mastered Ruby Accessors & Attributes!

Built-in Accessors

attr_reader, attr_writer, attr_accessor

Custom Accessors

Validation, formatting, computed values

Virtual Attributes

Computed properties and derived values

Ruby accessors provide elegant ways to manage object state. Use them wisely to create clean, maintainable interfaces while adding validation and formatting where needed.

Ruby Accessors & Attributes Mastery

Ruby Accessors & Attributes Mastery

Basic Accessor Methods

attr_reader - Read-Only Access

attr_writer - Write-Only Access

attr_accessor - Read/Write Access

Custom Accessor Methods

Custom Getter with Formatting

Custom Setter with Validation

Interactive Practice: Accessors & Attributes

Interactive Code Runner

Ruby Code Editor

Best Practices & Common Patterns

✅ Best Practices

❌ Common Pitfalls

Accessors & Attributes Mastery Summary

You've Mastered Ruby Accessors & Attributes!

Built-in Accessors

Custom Accessors

Virtual Attributes

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Related Topics

Video Tutorial

Ruby Language

Rails Framework

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Ruby Accessors & Attributes Mastery

Ruby Accessors & Attributes Mastery

Basic Accessor Methods

attr_reader - Read-Only Access

attr_writer - Write-Only Access

attr_accessor - Read/Write Access

Custom Accessor Methods

Custom Getter with Formatting

Custom Setter with Validation

Interactive Practice: Accessors & Attributes

Interactive Code Runner

Ruby Code Editor

Best Practices & Common Patterns

✅ Best Practices

❌ Common Pitfalls

Accessors & Attributes Mastery Summary

You've Mastered Ruby Accessors & Attributes!

Built-in Accessors

Custom Accessors

Virtual Attributes

Quick Navigation

Related Topics

Video Tutorial